1. Field of the Invention
The invention relates to a turbocharger for an internal combustion engine. More particularly, the invention relates to a turbocharger with a rotating electric machine, which includes a rotating electric machine such as an electric motor or an electric motor-generator.
2. Description of the Related Art
A turbocharger with a rotating electric machine is generally configured to include a rotating member of the turbocharger in which a shaft, that supports a turbine rotor at one end and a compressor impeller at the other end and that supports a rotor of the rotating electric machine at an intermediate portion, is supported by bearings, each of which has an inner race and an outer race, at a portion between the one end and the intermediate portion and a portion between the other end and the intermediate portion. Japanese Patent Laid-Open Publication No. 2000-145469 discloses a technology in which a rotor of a rotating electric machine is reinforced by being covered with a reinforcing sleeve in order to prevent damage to a magnet constituting the rotor of the rotating electric machine caused by a strong centrifugal force due to high speed rotation of a rotating member of a turbocharger, in a turbocharger with a rotating electric machine having the above-mentioned configuration. Also, this publication discloses a technology in which a tube-like spacer is provided in each of a portion between one end of the rotor of the rotating electric machine and a bearing adjacent thereto and a portion between the other end of the rotor of the rotating electric machine and a bearing adjacent thereto, in order to maintain an axial position of the rotor of the rotating electric machine in the rotating member of the turbocharger.
Meanwhile, heat due to eddy currents is generated in a rotor of a rotating electric machine. Accordingly, Japanese Patent Laid-Open Publication 2001-25209 discloses a technology in which a spiral hole penetrating the rotor in the axial direction is formed in the rotor and air or a cooling medium flows through the spiral hole.
In order to stably operate a turbocharger with a rotating electric machine, it is requested that heat generated in the rotating electric machine be appropriately released. It is also requested that a magnet of a rotor of the rotating electric machine containing relatively brittle material be protected from damage due to a centrifugal force, an axial position of the rotor of the rotating electric machine be stably maintained in the rotating member of the turbocharger, and the like. Namely, these requests to the turbocharger with a rotating electric machine need to be satisfied with a simple configuration.